Many cities are embarking on coordinated programs designed to significantly increase their tree cover, in order to address issues such as aesthetics, energy use, carbon sequestration, air quality, and stormwater runoff. Some of those efforts will be good stories this spring as trees go in the ground, or as planning efforts take root. Others will be interesting as grand plans run into realities such as who will pay, which trees will work best, who will do the planting, where the trees will go, and who will maintain them.

One perspective on the dollar value of trees has recently been provided by New York City, which determined after a multi-year process that each dollar spent on a street tree returns $5.60 in benefits, such as cleaner air, reduced energy consumption, and increased property values. The study, by researchers from the University of California, Davis, and the US Forest Service who used a program called Stratum, covered about 592,000 street trees, but not the additional 4.5 million trees on parks and private lands. (Media coverage,[2] New York Times, April 18, 2007, by David Randall.) A couple of starting points for learning more about urban forestry in NYC are: Dept. of Parks & Recreation[3] and Trees New York.[4] On April 22, 2007, Mayor Michael Bloomberg announced his PlaNYC for a greener NYC, which includes proposals (that still need to be approved) to plant more than one million trees along streets and in parks by 2017 (PlaNYC Air Initiatives[5]).

Some of the other substantial urban forestry efforts are occurring in:

SACRAMENTO, whose Greenprint[6] program involves 22 cities and 4 counties in a multi-decade effort to plant up to five million trees.

LOS ANGELES, where the Million Trees LA[7] campaign is designed to increase the current canopy cover of 18% to the national average of 27% in a relatively arid area. There is no timeline, and any tree species is allowed. The project involves a wide spectrum of government, institutional, and individual players, on public and private land.

SEATTLE,[11] which is just getting underway in its efforts to plant about 650,000 trees in the next 30 years, to help offset the effects of a slash in its tree canopy from 40% 35 years ago to 18% now. Office of Sustainability and Environment,[12] 206-615-0817. Media coverage,[13]Seattle Post-Intelligencer, Sept. 6, 2006, by Lisa Stiffler.

A starting point for cities not mentioned above (as well as some that were mentioned): the Alliance for Community Trees' list of 115 members[25]in the US and Canada; Jared Liu,[26] 301-220-3279.

Whatever the city, a useful tool to know about is the Urban Forest Effects Model,[27] which assesses selected environmental effects of urban trees. It has been used in cities such as Atlanta, Baltimore, Boston, Calgary, Jersey City, New York City, Philadelphia, Syracuse, and Toronto.

In one recently completed application of the tool (called UFORE), researchers at the SUNY College of Environmental Science and Forestry developed for Syracuse[28] a palette of 31 preferred trees, an appropriate mix, and associated management practices, to best balance air quality and carbon sequestration while considering other factors such as function, species diversity, disease resistance, invasiveness, and native occurrence. Getting the details right is important, the team says, because trees vary substantially in their ability to sequester carbon, and in their emissions of harmful pollutants, with the effects sometimes exacerbated by interactions with typical urban pollutants.

The same refined application of UFORE, which was used for the first time in this effort and ended up recommending less than half the tree species commonly found in the city, can be used in any city that has available UFORE data, according to the team.